1. Field of the Invention
The present invention relates to a novel tape cassette and, more specifically, to a tape cassette having a front lid covering a space extending in front of the magnetic tape contained therein and a back lid covering a space extending behind the magnetic tape.
2. Description of the Prior Art
Importance of protecting a magnetic tape from dusting has increased with the augmentation of recording density. Some tape cassette is provided with a front lid and a back lid for covering spaces extending in front of and behind, respectively, of the magnetic tape contained therein so that the magnetic tape will not be exposed while the magnetic tape is not in use. Such a tape cassette a is shown in FIGS. 1 to 12. This tape cassette a has a case body b resembling a box having a laterally elongate, rectangular shape in plan view. Two tape reels, not shown, are supported for rotation within the case body b. A magnetic tape c having opposite ends fastened respectively to the tape reels extends along the front surface of the case body b between tape outlets, not shown, formed in the front wall of the case body b. The case body b is provided with a mouth d having an upper opening and a front opening and formed in front of the front wall thereof between the two tape outlets.
A front lid e for covering the a space extending in front of the case body b is supported pivotally on the case body b. The front lid e has a front wall f facing the front wall of the case body b, an upper wall g extending backward from the upper edge of the front wall f, side walls h (only one of them is shown) extending backward from the opposite side edges of the front wall f, and trunnions i (only one of them is shown) projecting from the side walls h and rotatably supported in holes formed in the respective front portions of the side walls of the case body b. The front lid e is rotatively biased by a spring, not shown, toward a closing position, where the front wall f of the front lid e is positioned in front of a portion of the magnetic tape c extending along the front surface of the front wall of the case body b. Support legs j (only one of them is shown) project downward from the upper wall g of the front lid e at positions at a small distance from the opposite side ends of the upper wall g and corresponding to the opposite ends of the mouth d.
A back lid k is positioned in the mouth d so as to cover the back surface of the magnetic tape c. Pivots 1 (only one of them is shown) projecting from the substantially central portions of the opposite side walls of the back lid k are supported pivotally on the lower ends of the support legs j, respectively, of the front lid e. The back lid k has side walls provided at their lower ends with projections m (only one of them is shown). The projections m are fitted in guide grooves n (only one of them is shown) formed in side walls defining the opposite ends of the mouth d of the case body b, respectively. The back lid k has an upper wall o which extends horizontally when the back lid k is at the closing position.
In FIG. 10, the front lid e and the back lid k are at their closing positions, where the front wall f of the front lid e is positioned in front of the exposed portion of the magnetic tape c and the back lid k is behind the exposed portion of the magnetic tape c in the mouth d. In this state, the front half of the upper opening of the mouth d is covered with the upper wall g of the front lid e and the back half of the same is covered with the upper wall o of the back lid k. If the upper wall g of the front lid e is formed so as to cover the upper opening of the mouth d entirely, the height of the front lid e from the upper surface of the case body b when the front lid e is fully opened needs to be greater than that of the same having the upper wall g covering the front half of the upper opening of the mouth d, because the front lid e is turned about an axis and the front lid e must be positioned over the back lid k when the front lid e and the back lid k are fully opened. When the front lid e and the back lid k are fully opened, the upper wall o of the back lid k is positioned behind the upper wall g of the front lid e.
As a cassette holder holding the tape cassette a is lowered in the cassette loading unit of a video tape recorder, the lid opener p of the video tape recorder engages the lower edge of one of the side walls h of the front lid e as shown in FIG. 10. As the cassette holder is lowered further, the lid opener p pushes the front lid e to turn the front lid e on its trunnions i toward the opening position against the force of the spring biasing the front lid e toward the closing position as shown in FIG. 11. Finally, the front lid e is turned to the opening position as shown in FIG. 12. Meanwhile, the pivots 1 of the back lid k engaging the support legs j of the front lid e move upward together with the front lid e and the projections m of the back lid k move along the guide grooves n, turning the back lid k on the pivots 1 as the front lid e is turned on its trunnions i. The front lid e and the back lid k reach their opening positions simultaneously.
The front lid e of this tape cassette a has a relatively low rigidity and is liable to flex when pressure is applied to the middle portion thereof, because the front lid e consists of only the front wall f, the upper wall g and the side walls h. If the front lid e flexes, a gap is formed between the front lid e and the back lid k. Then, dust enters the tape cassette a and makes the magnetic tape c dusty or the magnetic tape c may possibly be damaged with fingers. Even if the magnetic tape c is not damaged accidentally or not made dusty, the user will worry about damaging the magnetic tape c and the reliability of the tape cassette a will be spoiled if a gap is formed between the front lid e and the back lid k.